Metabolic water

In chemical conversions of hydrogen- compounds with oxygen arises in many cases water. This water is called oxidation water. If this water formed by living organisms biochemically, so the term metabolic water is in use.

Summary

The combustion of fossil fuels such as natural gas and oil always even large amounts of water being produced. For cars with gasoline engines, the three-way catalyst for substantially complete combustion provides, so that water vapor the main component of car exhaust is. This newly formed water can be seen on cool days in the form of gas clouds.

Of special significance is the oxidation of water produced by the breakdown of nutrients (fats, carbohydrates and proteins) in the cells of animals and humans in cell metabolism. This metabolic water is available through the tissue fluids and blood of the whole body are available. In an adult man, one starts from day 250 to 300 ml of water oxidation. In many desert animals this water contributes very significantly to the water supply to the body, so that some species can survive without additional water intake for weeks ( see figure and water balance). As an example, the genus of kangaroo rats ( Dipodymis ) is called, in the oxidation of water up to 90% of the water balance covers.

Water oxidation in energy metabolism

As glucose degradation ( catabolism )

Both in animals and in plants is glucose (dextrose ) is the most important source of energy in cellular metabolism. It is made ​​available to the cells of the human being as blood sugar available. With complete oxidative degradation then the well-known equation of net respiration ( dissimilation ) applies:

The degradation of 1 mol glucose = 180 g accordingly leads to the formation of six moles of water = 6:18 g = 108 g of water. Per gram of glucose degraded after 108 g/180 g = 0.6 g water thus produced about 0.6 ml

For fat loss

Fats ( chemically triglycerides) are very common in plants reserve substances in fruits, seeds and other plant parts. Animals and humans store energy reserves in adipose tissues. To simplify fat is equated with pure tripalmitin in the sample calculation. If this fat mobilized and completely degraded by oxidation, then the following net equation is:

So: 2 mol tripalmitin = 2.807, 35 g = 1614.7 g yield the complete degradation of 98 mol of water = 98.18 g = 1764 g = 1.7 liters. Per gram of fat so created in 1764 g/1614, 7 grams = 1,092 grams, or about 1.1 ml of liquid water oxidation.

Oxidation of water during the combustion of fossil fuels

Oil and natural gas consists mainly of hydrogen-containing compounds. In addition to their complete combustion carbon dioxide produces a lot of water oxidation. Contrast, coal contains little hydrogen compounds is therefore arises only little water - but even more carbon dioxide. As an example here is to estimate how much water is newly created by the combustion of one liter of gasoline. For gasoline (114 g · mol -1 ) is assumed to simply as pure octane with the density 0.703 g · cm -3.

This results in the equation:

Of 2 mol of octane = 2.114 g = 228 g So 18 moles of water = ( 18:18 g ) results = 324 g The combustion of 1 liter of octane = 703 g/114 g = 6.1634 mol causes the formation of ( 6.1634 · 18 mol ) / 2 = 998 g of water, ie 1 liter of liquid water.

About the resulting emissions of carbon dioxide is much discussed because of its impact on climate ( greenhouse effect). In contrast, the influence of water formed simultaneously on the global climate is controversial or unclear. It is undisputed, however, that water is a particularly potent greenhouse gas, far more potent than carbon dioxide. However, since the content of the air to water vapor (relative humidity ) depends on temperature and air pressure, the water content of the air changes greatly and the newly formed water is included in the water cycle. On the other hand, the air in rising average temperatures increasingly more water vapor, which can lead to a positive feedback of the anthropogenic greenhouse effect ( Run-away effect). Discussed here is the extent to which the expected increased cloud formation can counteract this influence.